EP1466336A1

EP1466336A1 - Method for determining wear of a switchgear contacts

Info

Publication number: EP1466336A1
Application number: EP20020799097
Authority: EP
Inventors: Gilles Baurand; Jean-Christophe Cuny; Stéphane Delbaere
Original assignee: Schneider Electric Industries SAS
Current assignee: Schneider Electric Industries SAS
Priority date: 2001-12-21
Filing date: 2002-12-17
Publication date: 2004-10-13
Anticipated expiration: 2022-12-17
Also published as: RU2004122421A; RU2297065C2; FR2834120B1; US7109720B2; NO325543B1; FR2834120A1; NO20042941L; AU2002364323A1; ATE437444T1; JP4112497B2; US20050122117A1; KR20040071241A; ES2327220T3; WO2003054895A1; CN1618110A; EP1466336B1; DE60233074D1; KR100926394B1; CN1261951C; JP2005513729A

Abstract

The pole contact (C1,C2,C3) wear determination method has an electromagnet (20) with movement controlled by a field coil (21). Wear is determined on the basis of the contact wear stroke produced during a movement closing the electromagnet. An electric signal is measured on the conducting status of a power pole, by measuring the excitation current flowing in the coil on a time basis. The measured wear time is then compared with the initial travel time.

Description

Method for determining the wear of the contacts of a switching device

The present invention relates to a method for determining the wear of pole contacts in a power switch device provided with one or more power poles, in particular in a contactor, a choke or discontactor, or a circuit breaker contactor. The invention also relates to a switching device capable of implementing such a method.

A switching device has, on each power pole, fixed contacts and movable contacts, in order to switch an electrical load to be controlled. The pads mounted on these contacts wear more or less during each switching, depending on the current or voltage load. After a high number of switching operations, this wear can lead to a failure of the switch device, the consequences of which can be significant in terms of safety and availability. To prevent such consequences, a usual solution consists in systematically changing either the contacts or the entire switch device, after a predetermined number of operations (for example a million operations), without examining the actual wear of the pads. of contacts. This can therefore lead to late interventions if the pellets are already too worn or premature if the pellets are not yet sufficiently worn. The ability to be able to determine the actual wear of the contacts in order to deduce therefrom information giving the ^' residual service life or information giving the end of life of the pole contacts therefore provides an appreciable advantage in the case of a switching device. performing a large number of maneuvers since it allows the user to be alerted at the desired time and thus to prevent breakdowns or faults likely to occur in an automation installation.

In documents EP0878015 and EP0878016, the residual contact life is determined by calculating a change in contact pressure during a contact opening operation. The change in contact pressure is determined by measuring the time between the initial instant of movement of the armature of the control electromagnet and the final instant of contact opening. The initial instant is detected by an auxiliary circuit which analyzes the voltage across the electromagnet coil during the opening phase. The final instant corresponds to the start of the opening of the contacts of the most worn switching pole and is detected by connecting all the phases to a detection circuit and by measuring the switching voltage as voltage variation at an artificial neutral point of the downstream power lines.

However, the fact that these devices work on opening causes the presence of an electric arc which can disturb the voltage measurements in the poles. These devices also require special precautions to measure the coil voltage, such as the use of an auxiliary switch which must be added to isolate the auxiliary circuit from the coil supply so as to measure the coil voltage in discharge resistance.

The present invention aims to determine as simply as possible the wear of the pole contacts of a switching device while avoiding these drawbacks. For this, the invention describes a method for determining the wear of pole contacts in a switching device which comprises one or more power poles provided with contacts actuated by a control electromagnet whose movement between an open position and a closed position is controlled by an excitation coil, the contact wear being determined from a travel time of the contact wear stroke. According to the invention, the travel time of the contact wear stroke is developed, during a closing movement of the electromagnet, by measuring at least one electrical signal representative of the conductive state of at least one pole of power, by measuring an excitation current flowing in the solenoid coil and calculating the time difference between the instant of contact closure, determined from said electrical signal, and the instant of end of the movement of closing of the electromagnet, determined from said excitation current.

According to one characteristic, the instant of closing of the contacts is determined by the appearance of the electrical signal when the pole becomes conductive, and the end of the closing movement of the electromagnet determined by the detection of a minimum of the excitation current. .

According to another characteristic, the instant of closing of the contacts of each power pole is determined by the appearance of a main current flowing in the corresponding power pole of the switching device. According to another characteristic, the instant of closing of the contacts of a power pole is determined by the appearance, downstream of the contacts, of a phase / neutral voltage between the corresponding power pole and a neutral point. According to another characteristic, the instant of closing of the contacts of the power poles is determined by the appearance, downstream of the contacts, of a phase / phase voltage between two power poles.

Working to close the contacts, that is to say when controlling the electromagnet, and not to open the contacts has advantages. First of all, this avoids disturbances occurring during opening, linked in particular to the electric arc of the contacts and to the residual magnetic flux of the coil. This therefore simplifies the measurement of a current or a voltage in the poles of the device to detect the instant of contact closure. In addition, in a switching device whose coil is electronically controlled, the measurement of the excitation current of the coil is already carried out at the time of closing, during the control of the electromagnet, while it is not necessarily measured during opening. This measurement of the excitation current can therefore easily be used to additionally detect the end of the closing movement of the electromagnet.

The measured travel time of the wear stroke, possibly corrected by a correction coefficient, is used to determine the contact wear from the drift of this travel time measured compared to an initial travel time of the race. wear stored in memory means of the switch device. The wear of the contacts can also be determined from the comparison of the measured travel time of the wear stroke with a minimum acceptable travel time of the wear stroke stored in the memory means of the switching device.

The invention also describes a switch device capable of implementing this method. Such a switching device comprises first measuring means delivering at least one primary signal representative of the conductive state of at least one power pole, second measuring means delivering a secondary signal representative of an excitation current flowing in the coil of the electromagnet and a processing unit receiving the primary signal (s) and the secondary signal to implement the method. The first measuring means are placed in series on the current lines of the switching device, in order to measure the main currents flowing in the power poles. Alternatively, the first measurement means are placed between downstream current lines and a neutral point of the switching device, in order to measure the phase / neutral voltages of the power poles. According to another characteristic, the switch device comprises means for memorizing an initial travel time of the contact wear stroke. The processing unit calculates a measured travel time of the contact wear stroke, and compares said measured travel time with the stored initial travel time, in order to determine a residual contact life and / or to give end-of-life information beyond which product performance is no longer guaranteed.

Other characteristics and advantages will appear in the detailed description which follows with reference to an embodiment given by way of example and represented by the appended drawings in which: FIG. 1 shows a functional diagram of a switch device according to the invention comprising first current measurement means, FIG. 2 details in simplified fashion the operation of a contact pole in a switch device of FIG. 1,

FIG. 3 represents a series of diagrams showing the evolution of the main currents and of the excitation current during a closing movement of a switching device of FIG. 1.

- Figure 4 details an alternative to Figure 1 with first voltage measurement means.

An electrical switching device, for example of the contactor, contactor-circuit breaker or starter (discontactor) type, comprises one or more power poles. In the example of FIG. 1, the switch device has three power poles P1, P2, P3.

The switch device comprises upstream current lines (source lines), which establish the electrical continuity between the power supply network and the poles P1, P2, P3, and downstream current lines L1, L2, L3 (lines load) which establish the electrical continuity between the poles of the switch device and an electrical load, generally an electric motor M, which one wishes to control and / or protect thanks to the switch device. The upstream current lines are connected or disconnected from the downstream current lines by pole contacts C1, C2, C3. In known manner, the contacts C1, C2, C3 comprise movable contacts disposed on a movable bridge 28 and fixed contacts. The movable bridge 28 is actuated by a control electromagnet 20 and by a contact pressure spring 25. The control electromagnet 20 comprises a fixed yoke, a movable frame 23, a return spring 26 and an excitation coil 21. The closing movement of the movable armature 23 of the electromagnet 20 is generated by the passage of an excitation current Is in the excitation coil 21. Preferably the excitation coil 21 is supplied by a continuous excitation voltage.

In the embodiment detailed in FIG. 2, an interrupter pole switch device has been shown, but it could also be entirely envisaged that the device would have contactor poles. The operation of an apparatus with breaking poles is as follows: when no excitation current Is flows in the coil 21 of the electromagnet, the return spring 26 causes the separation between the movable armature 23 and the fixed yoke of the electromagnet. The movable frame 23 cooperates mechanically with a mechanical connection 22 not detailed here (such as a pusher) so as to act on the movable bridge 28, thus causing the opening of the contacts by separation of the movable contacts from the fixed contacts. The return spring 26 must for this have a force greater than that of the contact pressure spring 25. The appearance of an excitation current Is in the excitation coil 21 causes the reverse displacement of the movable armature 23 towards the fixed yoke of the electromagnet 20, thereby releasing the movable bridge 28. The contact closing force is then provided by the contact pressure spring 25 which presses on the movable bridge 28 to press the movable contacts against the contacts fixed. A device with breaking poles has the particular advantage of reducing the risk of rebound at the end of the closing movement of the contacts since, as the movable bridge 28 is detached from the movable armature 23 of the electromagnet at this point, This generally reduces the inertia of the moving movable bridge.

In a switch pole breaker device, it is possible to design by construction a thickness of the contact pads sufficient in such a way that the end of life of the product is not the consequence of too thin a thickness of the pads, but of a remaining contact wear stroke too small. Indeed, when this wear stroke becomes zero, this means that, when the movable armature 23 has finished its closing movement, the pusher 22 still remains in contact with the movable bridge 28 which hinders the pressure force that must exert the spring 25 to press the movable contacts against the fixed contacts. As the contact pressure is no longer sufficient, it is no longer possible under these conditions to guarantee proper operation of the switch device. Thus, the wear of the contacts can depend not on the remaining thickness of the pads, but on the remaining wear stroke of the contacts.

According to the invention, the switching device comprises first measuring means 11, 12, 13, 11 ′ capable of delivering at least one primary signal measuring at least one electrical signal representative of the conductive state of at least one pole of power P1, P2, P3. In the embodiment of FIG. 1, said first measuring means comprise current sensors 11, 12, 13 mounted in series on each downstream current line L1, L2, L3 and each delivering a primary signal, respectively 31.32 , 33, function of a main current Ip flowing in each pole, respectively P1, P2, P3 of the switching device. Usually, such current sensors 11, 12, 13 are used with the aim of ensuring in particular protection functions of the thermal fault, magnetic fault or short-circuit fault type in a contactor-circuit breaker. The current sensors 11, 12, 13 are for example Rogowski type current sensors. In this case, the primary signal obtained is actually an image of the derivative of the current Ip, which makes it possible to have an important signal as soon as the current appears, thus facilitating the detection of the instant of appearance of the current Ip. .

In the alternative embodiment of FIG. 4, the first measurement means 11 ′ are placed downstream of the contacts C1, C2, C3, between the downstream current lines L1, L2, L3 and a virtual neutral point N of the switch device, so as to deliver primary signals, respectively 31 ', 32 \ 33', function of the phase / neutral voltage of the different power poles, respectively P1, P2, P3. This alternative solution may prove to be simpler to implement in devices that do not have current sensors. In the simplified example of FIG. 4, the measuring means 11 ′ comprise in known manner, bypassing each pole measured, a first strong resistance, making it possible to lower the intensity of the current, placed in series with a second resistance whose terminal voltage is measured. The neutral point N joins the end of the second resistors. Other similar voltage measurement systems exist. After any analog processing, the measurement means 1 ′ therefore generate primary signals 31 ′, 32 ′, 33 ′, representative of the phase / neutral voltages of the different poles. In another alternative embodiment, one could also consider using first measurement means capable of measuring a phase / phase voltage between two power poles. The primary signals 31, 32, 33 or 31 ', 32', 33 'are sent to a processing unit 10 of the switching device. This processing unit 10 is for example located in an integrated circuit of the ASIC type, mounted on a printed circuit inside the switch device. It can in particular be used to control the control electromagnet 20 as well as, in the case of a contactor-circuit breaker, to control a thermal and / or magnetic trip device.

The switching device also includes second measurement means 14 for measuring the excitation current Is flowing in the excitation coil 21 of the electromagnet 20. As the coil 21 is supplied with DC voltage, the second measurement means 14 may be composed of a resistor connected in series on the control circuit of the coil 21, the voltage of which is measured directly at the terminals. After any analog processing of this measurement, the measurement means 14 therefore generate a secondary signal 34, representative of the excitation current Is, which is sent to the processing unit 10.

In the case of a switching device of the contactor / circuit breaker type which already has current sensors 11, 12, 13 measuring main currents Ip to ensure the protection of an electric charge, these same current sensors can then be advantageously used in the context of the present invention to also determine the time of closing of the contacts C1, C2, C3. In addition, if such a contactor / circuit breaker device already includes an electronic processing unit 10 responsible in particular for driving a control electromagnet 20, this processing unit 10 also has information 34 representative of the excitation current Is. It is then easy and economical to integrate into such a switching device a method for determining the wear of the contacts as described in the invention, so as to be able to alert the user at the desired time and thus prevent breakdowns or possible faults in the switching device.

With reference to FIG. 3, the method which is implemented in the processing unit 10 is based on the following principle:

When a control order 50 for closing the contacts appears, the excitation current Is, shown diagrammatically by the curve 51, sent to the coil 21 of the electromagnet 20 begins to increase. During this take-off phase, the frame mobile 23 of the electromagnet 20 still remains stationary and the excitation current Is increases, according to a substantially asymptotic curve.

Arrived at an instant A, the excitation coil 21 has stored enough ampere-turns to cause the closing movement of the movable armature 23 to start. From this instant, the air gap of the electromagnet 20 will gradually decrease, which will cause a variation in the reluctance of the magnetic circuit composed of the fixed yoke and the movable armature 23 of the electromagnet 20. This variation in the reluctance causes the excitation current Is to drop. This drop of the excitation current Is continues until an instant C corresponding to the end of the travel of the movable armature 23, that is to say at the end of the closing movement of the electromagnet 20. Au- beyond instant C, the air gap and therefore the reluctance of the electromagnet no longer vary and the excitation current Is begins to increase again, as indicated on curve 51.

In parallel, from moment A, the movement of the movable armature gradually releases the movable bridge 28 and this is then driven by the contact pressure spring 25. The movable bridge 28 then sets in motion until at an instant B where the movable contacts of each power pole will be pressed against the corresponding fixed contacts, causing the conductive state of the pole. From this instant B, a main current Ip measured by the various current sensors 11,12,13 will appear, as shown diagrammatically by curve 52. In the case where each pole has two fixed contacts and two movable contacts, as in FIG. 2, instant B advantageously corresponds to the closing of the two pairs of fixed / mobile contacts, which makes it possible to detect the greatest wear of the pads of the two pairs of contacts of the same pole. In the alternative embodiment of FIG. 4, the instant B can be determined on each pole by the appearance, downstream of the contacts, of a phase / neutral voltage measured by the first measuring means 11 'between a pole and the virtual neutral N. Likewise, the instant B could also be detected with a phase / phase voltage measurement between two of the poles of the device, downstream of the contacts.

Thus, the processing unit 10 is capable of detecting the end of the closing movement of the electromagnet, corresponding to the instant C, by detecting the appearance of a minimum of the excitation current Is, represented by a point of reversing on the curve Is of FIG. 3, from the secondary signal 34 received. On the other hand, the processing unit 10 is also capable of detecting the instant of closing of the contacts, corresponding to time B, by detecting the appearance of electrical signals representative of the conductive state of the poles (i.e. either main current Ip, or phase / neutral voltage, or phase / phase voltage) from primary signal (s) 31, 32,33 or 31 ', 32', 33 '. By comparing the variations of the electrical signal (s) and of the excitation current Is as a function of time, the processing unit 10 is able to determine the travel time of the contact wear stroke.

In fact, the time T1 between instant A and instant C corresponds to the duration of the closing movement of the movable armature 23 of the electromagnet. The time T2 between instant A and instant B corresponds to the duration of the closing movement of the movable bridge 28. The difference between T1 and T2, called Tu, corresponds to the travel time necessary to carry out the wear stroke of the contacts (also called contact overwriting stroke), between time B and time C, shown diagrammatically in diagram 53. It is obvious that the more the pads of the fixed and / or mobile contacts are worn, the more time T2 is important, and therefore the lower the time Tu. To avoid possible punctual inaccuracies in the measurements and the calculation of the time Tu, filtering or smoothing can easily be carried out by the processing unit 10 in particular by taking into account only average values calculated from a plurality of measurements carried out on a determined number of closing cycles of the electromagnet, for example of the order of a few tens of cycles.

Indifferently, the information relating to contact wear can include information on the residual life of the contacts, expressed as a percentage, in degrees of wear, etc., and or alert information indicating the end of life of the switch device contacts.

In order to draw up information on the residual lifetime of the contacts, the processing unit 10 compares the measured travel time Tu of the contact wear stroke with an initial travel time Ti corresponding to an initial wear travel of the contacts. contacts (also called crush stroke in new condition) and monitors the evolution over time of the difference between Tu and Ti. This initial travel time Ti corresponds to a calibration value, determined for a given type of electromagnet.

In order to prepare end-of-life alert information for the contacts, the processing unit 10 compares the measured travel time Tu of the wear stroke of the contacts with a minimum travel time Tmini corresponding to an acceptable minimum contact wear stroke below which it is no longer possible to guarantee the expected performance of the switch device. This minimum travel time Tmini is also determined for a given type of electromagnet. The switch device then has internal storage means

15 connected to the processing unit 10 and capable of storing this initial value Ti and / or this minimum value Tmini. The storage means 15 consist for example of a non-volatile memory of the EEPROM or Flash memory type. Advantageously, for reasons of cost and size, the processing unit 10 and the storage means 15 are installed in the same integrated circuit of the switching device. The initial value Ti is stored in the storage means 15 either with a predetermined value during the manufacture of the switching device, or with a first measurement of Tu carried out during the first switching operations of the switching device.

To compare Tu with Ti and / or Tmini, it is advisable to make an assumption on the real speed of the mobile part 23 of the electromagnet during the contact closure process. Indeed Ti and Tmini have been determined for example from a nominal speed of the movable part 23 of the electromagnet, and this nominal speed is not necessarily identical to the real speed having served to determine Tu.

In a first simplified variant, it is considered that the speed of movement of the movable armature 23 remains substantially constant for a given type of electromagnet of a given caliber. In this case, by monitoring the drift of the difference existing between the measured travel time Tu and the initial travel time Ti, the processing unit 10 is easily able to calculate the residual life of the contacts. Likewise, the processing unit 10 is easily capable of giving end-of-life information of the contacts, when Tu becomes less than Tmini, without requiring correction on the measurement of Tu.

In a second variant, it is considered that the speed of movement of the movable armature 23 depends not only on the type of electromagnet but also on the supply voltage of the excitation coil (or at least the voltage of average supply seen by the coil in the case of a cut-out control). Indeed, the higher the supply voltage, the greater the actual speed of movement of the movable armature 23 during the movement of closing. In this case, the switching device has means for measuring this supply voltage. These means are connected to the processing unit 10, allowing the latter to assign a correcting coefficient taking the variations in speed to the measured travel time Tu, before making a comparison with Ti and / or Tmini , so as to obtain better precision in the preparation of information relating to contact wear.

In a third variant, it is considered that the speed of movement of the movable armature 23 also depends on other parameters, such as the operating temperature of the device. However, the process should not be penalized with calculations that would become too complex. This is why, in this case, to more precisely estimate the speed of movement of the movable armature 23, the processing unit calculates a duration of the take-off phase T3 (see FIG. 3) which corresponds to the time elapsed between a instant O of the appearance of a current Is in the coil and the instant determined by the maximum of the current Is, when the movement of the movable armature 23 starts to start. This duration T3 is also a function of the operating temperature of the device and the supply voltage of the coil, one can then make a simple correlation between the variation of the duration T3 and the variation of the speed of the movable armature. By comparing the duration T3 measured with a stored reference duration, a correction coefficient can be assigned to the measured travel time Tu, taking into account the variations in speed, in order to obtain better precision in the preparation of the information relating to contact wear.

The switch device further comprises communication means 18 which make it possible to connect it to a communication bus B, such as a serial link, a field bus, a local network, a global network (of the Intranet or Internet type). Or other. These communication means 18 are connected to the processing unit 10 so that information relating to the wear of the pole contacts calculated by the processing unit 10 can be transmitted on the communication bus B. The switch device also includes signaling means 17 connected to the processing unit 10. These signaling means 17, such as a mini screen or one or more LEDs on the front face of the switch device, allow an operator located close to the switch device to display information relating to the wear of the pole contacts calculated by the processing unit 10. Furthermore, in the case where the processing unit 10 is responsible for controlling the control electromagnet 20 by means of a control command, the processing unit 10 is capable of slaving this control command to information end of life of the pole contacts, so as to be able to lock any possibility of closing the power poles of the switch device in the event of excessive wear of the contacts, since this would no longer be able to guarantee the advertised performance of the switch device. This provides a very significant additional security function, since the switch device can self-lock in the event of a risk of malfunction.

In a preferred embodiment, the switching device has a current sensor 11, 12, 13 for each of its power poles P1, P2, P3. The processing unit 10 then receives as many primary signals 31, 32, 33 as there are poles and is therefore capable of separately detecting the wear of the contacts on each power pole. In this case, the wear of the switch device contacts will be calculated either pole by pole, or by taking the power pole whose contacts are the most worn.

In another embodiment, the switch device does not have a current sensor 11, 12, 13 in each pole P1, P2, P3 of power, but has for example a current sensor only for a single pole. The processing unit 10 then receives a single primary signal and is only capable of actually detecting the wear of the contacts of this power pole. In this case, the wear of all the contacts of the switch device will be determined from this single measurement for one pole, without taking into account any disparities between the wear of the different poles.

It is understood that one can, without departing from the scope of the invention, imagine other variants and refinements of detail and even consider the use of equivalent means.

Claims

1. Method for determining the wear of pole contacts (C1, C2, C3) in a switching device which comprises one or more power poles provided with contacts actuated by a control electromagnet (20) whose movement between an open position and a closed position is controlled by an excitation coil (21), the contact wear being determined from a travel time (Tu) of the contact wear stroke (C1, C2, C3), characterized by the fact that the travel time (Tu) of the contact wear stroke is developed, during a closing movement of the electromagnet:

By measuring at least one electrical signal (Ip) representative of the conductive state of at least one power pole (P1, P2, P3),

• by measuring an excitation current (Is) flowing in the coil (21) of the electromagnet (20), “by calculating the time difference between the contact closing instant, determined from said electrical signal ( Ip), and the instant of end of the closing movement of the electromagnet, determined from said excitation current (Is).

2. Method according to claim 1, characterized in that the instant of end of the closing movement of the electromagnet is determined by the detection of a minimum of said excitation current (Is).

3. Method according to claim 2, characterized in that the instant of closing of the contacts (C1, C2, C3) is determined by the appearance of said electrical signal (Ip).

4. Method according to claim 2, characterized in that the instant of closing of the contacts (C1, C2, C3) of each pole is determined by the appearance of a main current (Ip) flowing in each power pole (P1, P2, P3) of the switch device.

5. Method according to claim 2, characterized in that the instant of closing of the contacts (C1, C2, C3) of each pole is determined by the appearance, downstream of the contacts, of a phase / neutral voltage between each power pole (P1, P2, P3) and a neutral point (N).

6. Method according to claim 2, characterized in that the instant of closing of the pole contacts (C1, C2, C3) is determined by the appearance, downstream of the contacts, of a phase / phase voltage between two power poles (P1.P2.P3).

7. Method according to one of claims 1 to 6, characterized in that the wear of the contacts is determined from the evolution of the measured travel time (Tu) of the wear stroke of the contacts relative to an initial travel time (Ti) of the contact wear stroke stored in the storage means (15) of the switching device.

8. Method according to one of claims 1 to 6, characterized in that the wear of the contacts is determined from the comparison of the measured travel time (Tu) of the wear stroke of the contacts with a time of minimum acceptable course (Tmini) of the contact wear stroke stored in the storage means (15) of the switching device.

9. Switching device comprising one or more power poles

(P1.P2.P3) provided with contacts (C1.C2.C3) which are actuated by a control electromagnet (20) whose movement is controlled by an excitation coil (21), characterized in that the switch device includes:

• first measurement means (11, 12, 13, 11 ') delivering at least one primary signal (31, 32, 33, 31', 32 ', 33') representative of the conductive state of at least one pole power (P1.P2.P3),

• second measurement means (14) delivering a secondary signal (34) representative of an excitation current (Is) flowing in the coil (21) of the electromagnet (20), • a processing unit (10) capable of receiving the primary signal (s)

(31, 32, 33, 31 ', 32', 33 ') and the secondary signal (34), making it possible to implement the method according to one of the preceding claims.

10. Switching device according to claim 9, characterized in that the first measuring means (11, 12,13) are placed in series on current lines (L1, L2, L3) of the switching device, in the purpose of measuring the main currents (Ip) flowing in the power poles (P1.P2.P3).

11. Switching device according to claim 9, characterized in that the first measuring means (11 ') are placed between downstream current lines (L1.L2.L3) and a neutral point (N) of the switching device, in order to measure the phase / neutral voltages of the power poles (P1.P2.P3).

12. Switching device according to claim 10 or 11, characterized in that it comprises storage means (15) capable of storing an initial travel time (Ti) of the contact wear stroke.

13. Switching device according to claim 12, characterized in that the processing unit (10) calculates a measured travel time (Tu) of the contact wear stroke (C1.C2.C3), and compares said measured time (Tu) with the initial travel time (Ti) memorized, to determine information relating to the wear of the pole contacts.

14. Switching device according to claim 13, characterized in that the processing unit (10) and the storage means (15) are located in an integrated circuit of the switching device.

15. Switching device according to claim 13, characterized in that it comprises communication means (18) connected to the processing unit (10) for transmitting on a communication bus (B) information relating to the wear of pole contacts.

16. Switching device according to claim 13, characterized in that it comprises signaling means (17) connected to the processing unit (10) making it possible to display information relating to the wear of the pole contacts.

17. Switching device according to claim 13, in which the processing unit (10) issues a control command to the electromagnet (20), characterized in that the processing unit (10) is capable of controlling the control order of the electromagnet (20) to information relating to the wear of the pole contacts.